Research Roundup: Findings on BPA
More News about BPA
In early September, the National Toxicology Program (NTP) released its final report on bisphenol A, or BPA, a synthetic chemical found in, among other things, polycarbonate plastic containers and the epoxy linings of canned foods. Humans are exposed to BPA throughout their lifetimes and many scientists have expressed concern that this repeated exposure may have negative health consequences. But study findings have been somewhat controversial since research so far has been conducted with rodents and may not represent what happens in humans.
The NTP report found that human exposure to BPA is of “some concern” when it comes to its effects on prostate and brain development and for behavioral effects in fetuses, infants and children. The report also expresses “minimal concern” that exposure affects mammary gland development or early puberty in females. The report states “negligible concern” that exposure during pregnancy can result in fetal or infant mortality, birth defects or reduced birth weight. For the full report, visit www. cerhr.niehs.nih.gov.
Around the same time the NTP report was released, researchers at the Yale School of Medicine announced that BPA causes the loss of synapses, or connections, between nerve cells in monkeys. The primates were given a daily dose equivalent to the amount the U.S. Environmental Protection agency sets as its “reference dose,” or the safe upper limit for human beings.
In humans, alterations in the number of synapses “appear to play critical roles in some neurologic/neuropsychiatric disorders, including mental retardation and developmental disabilities, Alzheimer’s disease, schizophrenia, and mood disorders,” writes lead author Csaba Leranth, MD, professor of obstetrics, gynecology and reproductive sciences and of neurobiology. The ability of BPA to interfere with synapse formation has “profound implications,” the authors write. The study, published in the Proceedings of the National Academy of Sciences, underscores concerns about “the widespread use of BPA in medical equipment, and in food preparation and storage.”
In another study, researchers at the University of Cincinnati, led by Nira Ben-Jonathan, PhD, professor of cancer and cell biology, have found that BPA suppresses a hormone responsible for regulating insulin sensitivity in humans. The hormone, adiponectin, also helps control tissue inflammation and it reduces the risk of developing metabolic syndrome, a group of conditions that include obesity and high blood pressure. Metabolic syndrome is associated with a higher risk of diabetes and heart disease. The study, published in Environmental Health Perspectives, was conducted on human fat tissue. Samples were taken from patients undergoing surgery.
And researchers at Peninsula Medical School in Exeter, United Kingdom, found that increased concentrations of BPA in human urine were associated with greater odds of developing cardiovascular disease, diabetes and abnormal levels of certain liver enzymes. The study used data from the U.S. National Health and Nutrition Examination Survey (NHANES) 2003–2004. The survey included more than 1,400 adults, ages 18 to 74, with measured urinary BPA levels. Survey participants with the highest BPA levels had nearly three times the odds of cardiovascular disease compared to subjects with the lowest levels. They also had 2.4 times the odds of diabetes compared with those with lower levels.
The findings don’t prove causality, the authors explain. Additional studies are still needed.
In an editorial accompanying the article, published in the Journal of the American Medical Association, Frederick vom Saal, PhD, of the University of Missouri, Columbia, and John Peterson Myers, PhD, of Environmental Health Sciences, Charlottesville, Virginia, write that, “While preliminary with regard to these diseases in humans,” the results should “spur U.S. regulatory agencies to follow the recent action taken by Canadian regulatory agencies, which have declared BPA a ‘toxic chemical’ requiring aggressive action to limit human and environmental exposures.” Alternatively, the writers suggest, “Congressional action could follow the precedent set with the recent passage of federal legislation designed to limit exposures to another family of compounds, phthalates, also used in plastic. Like BPA, phthalates are detectable in virtually everyone in the United States.”
According to the Center for Science in the Public Interest, consumers can reduce exposure to BPA by avoiding no. 7 plastics (not all contain BPA, however); by preparing and storing food in glass, porcelain or stainless steel containers; and by buying foods that are fresh, frozen or packaged in boxes rather than in cans. In addition, the Center recommends against microwaving polycarbonate plastic bottles (such as baby bottles and water bottles), washing them in the dishwasher or filling them with hot liquids.
Linking Lyme and Autism
A group of doctors, led by Robert Bransfield, MD, have published an article exploring a possible link between tick-borne illnesses, such as Lyme disease, and autism spectrum disorders.
“An association between Lyme disease and other tick-borne infections (TBI) during fetal development and in infancy with autism, autism spectrum disorders (ASD) and autistic symptoms has been noted by numerous clinicians and parents,” the authors write. “Since environment changes faster than genes, the rapidly emerging epidemic and geographical spread of ASD suggests significant environmental contributors, that may include infections.”
Published in Medical Hypotheses, the article brings together findings from presentations at a recent Lyme Induced Autism Foundation conference with other sources addressing the potential association. Some of these sources included peer-reviewed literature, databases of medical articles, U.S. government statistics, unpublished data, Internet searches and clinical observations.
The authors write that a number of doctors have noted multiple cases of mothers with tick-borne illnesses and children with ASD, infants with TBI who also had autistic symptoms and children with ASD whose symptoms worsened after being infected with a tick-borne illness. Other reports have noted ASD symptom improvement in children receiving antibiotics for infections. In addition, three small pilot studies showed that between 20 and 30 percent of ASD patients tested positive for the bacterium that causes Lyme disease. The authors also looked at reports of brain imaging research and geographical pattern analysis.
If a link between the two diseases is proven and accepted, the authors write, screening pregnant women for TBI and providing appropriate treatment may help reduce the incidence of ASD.
Genetic Clues to Treating Autism
Scientists have identified several genes that may play a role in autism but the disorder is so complex and symptoms vary so much that much work remains to be done. An international collaboration led by Christopher Walsh, MD, PhD, chief of the division of neurogenetics at Beth Israel Deaconess Medical Center in Boston and an investigator with the Howard Hughes Medical Institute, has found six genes that play a role in autism when mutated. The group’s work was published in Science.
The team focused on large families in which both parents shared a recent ancestor. The researchers compared the genomes of autistic and non-autistic siblings in these 88 families. Their findings suggest new possibilities for potential treatments of autism. In some cases, gene therapy might eventually offer a solution. In other cases, depending on the patient’s genetic makeup, certain types of training or learning environments might work best.
Walsh and colleagues plan to continue to analyze their data. “The more we understand about the control of these genes, the more we can help a lot of different kids.” LW